Hi Thomson, It seems that your problem is the CONFIG_DEBUG_RODATA option was enabled, It is recommend to turn CONFIG_DEBUG_RODATA off when using kgdb.
From the kgdb document(DocBook/kgdb.tmpl): If the architecture that you are using supports the kernel option CONFIG_DEBUG_RODATA, you should consider turning it off. This option will prevent the use of software breakpoints because it marks certain regions of the kernel's memory space as read-only. If kgdb supports it for the architecture you are using, you can use hardware breakpoints if you desire to run with the CONFIG_DEBUG_RODATA option turned on, else you need to turn off this option. Thanks, Dongdong Thomson, Patrick S wrote: > Hi Folks, > > I'm wondering if anyone has had issues with setting breakpoints. I'm > able to break into the kernel, access data, do a backtrace, etc, but > when I attempt to set a breakpoint, then continue, I get the following error: > > Cannot insert breakpoint 1. > Error accessing memory address 0xffffffff81310931: Unknown error 4294967295. > > I'm attaching a sample session, I had set remote debug to 1 > > Thanks! > Pat Thomson > > [pstho...@psthomso-desk2 linux-2.6.36-rc6-kgdb]$ gdb ./vmlinux > GNU gdb (GDB) Fedora (7.0.1-45.fc12) > Copyright (C) 2009 Free Software Foundation, Inc. > License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html> > This is free software: you are free to change and redistribute it. > There is NO WARRANTY, to the extent permitted by law. Type "show copying" > and "show warranty" for details. > This GDB was configured as "i686-redhat-linux-gnu". > For bug reporting instructions, please see: > <http://www.gnu.org/software/gdb/bugs/>... > Reading symbols from > /home/psthomso/Kernels/linux-2.6.36-rc6-kgdb/vmlinux...done. > (gdb) show architecture > The target architecture is set automatically (currently i386:x86-64) > (gdb) set debug remote 1 > (gdb) target remote /dev/ttyS1 > Remote debugging using /dev/ttyS1 > Sending packet: $qSupported#37...Sending packet: $qSupported#37...Sending > packet: $qSupported#37...Sending packet: $qSupported#37...Timed out. > Timed out. > Timed out. > Ignoring packet error, continuing... > Packet qSupported (supported-packets) is supported > warning: unrecognized item "timeout" in "qSupported" response > Sending packet: $Hg0#df...Sending packet: $Hg0#df...Sending packet: > $Hg0#df...Sending packet: $Hg0#df...Ack > Packet received: OK > Sending packet: $?#3f...Ack > Packet received: S05 > Sending packet: $Hc-1#09...Ack > Packet received: OK > Sending packet: $qC#b4...Ack > Packet received: QC00000000fffffffd > Sending packet: $qAttached#8f...Ack > Packet received: > Packet qAttached (query-attached) is NOT supported > Sending packet: $qOffsets#4b...Ack > Packet received: > Sending packet: $g#67...Ack > Packet received: > 140000000000000067000000000000000af00000000000000000e4010088ffff46000000000000004600000000000000c839e4010088ffffc839e4010088ffff0000000000000000730000000000000000dcca3f0288ffffc844c081ffffffff0030ef3f0288ffff7019a281ffffffff04000000000000009600000000000000cba40881ffffffff020000001000000018000000 > kgdb_breakpoint (key=70, tty=0x46) at kernel/kgdb.c:1749 > 1749 wmb(); /* Sync point after breakpoint */ > Sending packet: $qSymbol::#5b...Ack > Packet received: > Packet qSymbol (symbol-lookup) is NOT supported > (gdb) bt > Sending packet: $mffff880001e439c0,40#5e...Ack > Packet received: > c0a40881ffffffff183ae4010088fffffe972b81ffffffff82000000000000000100000000000000f839e4010088ffff220000000000000000dcca3f0288ffff > Sending packet: $mffff880001e43a00,40#53...Ack > Packet received: > 01000000000000000030ef3f0288ffff0100000000000000283ae4010088ffff1c992b81ffffffff983ae4010088ffff391f2b81ffffffff983ae4010088ffff > Sending packet: $mffff880001e43a80,40#5b...Ack > Packet received: > 220000000000000001000000000000000100000000000000e83ae4010088ffff80413681ffffffff010000000000000090b93a3f0288ffff2200000000000000 > Sending packet: $mffff880001e43ac0,40#86...Ack > Packet received: > 00b03a3f0288ffff2200000000000000010000000000000001000000000000000100000000000000383be4010088ffff51613681ffffffff2ece17c964080000 > Sending packet: $mffff880001e43b40,40#58...Ack > Packet received: > 53623681ffffffff883be4010088ffff0200000000000000883be4010088ffff1081383f0288ffff00b03a3f0288ffff01000000000000000080383f0288ffff > Sending packet: $mffff880001e43b00,40#54...Ack > Packet received: > 0100000001000000310000000288ffff00b03a3f0288ffff0100000000000000f8b73a3f0288ffff22000000000000000100000000000000883be4010088ffff > Sending packet: $mffff880001e43b80,40#5c...Ack > Packet received: > 0080383f0288ffffb83be4010088ffffe70c3a81ffffffff0080f83f0288ffff1081383f0288ffff0100000000000000204fa681ffffffff083ce4010088ffff > Sending packet: $mffff880001e43bc0,40#87...Ack > Packet received: > b2f53981ffffffffd83be4010088ffff4600000001000000083ce4010088ffff0080383f0288ffff603cf3430288ffff0080f83f0288ffff0400000000000000 > Sending packet: $mffff880001e43c00,40#55...Ack > Packet received: > 0000000000000000b83ce4010088ffff0dfa3981ffffffff0f2110ff0200ffff503ce4010088ffff8000000000ffffff0058753f0288ffff18c9cd4f0288ffff > Sending packet: $mffff880001e43cc0,40#88...Ack > Packet received: > adfc3981ffffffffcc8d0181ffffffff07f081370088ffff0100000000000000204fa681ffffffff2d4e0681ffffffff00c0713f0288ffff80c4483f0288ffff > Sending packet: $mffff880001e43c80,40#5d...Ack > Packet received: > 0100000000000000b83ce4010088ffff0080f83f0288ffff0058753f0288ffff00a8fb3f0288ffff00f081370088ffff0800000000000000183de4010088ffff > Sending packet: $mffff880001e43d00,40#56...Ack > Packet received: > 0080f83f0288ffff0004e83f0288ffff0000000000000000583de4010088ffff05a63a81ffffffff383de4010088ffff80c4483f0288ffff0000000000000000 > Sending packet: $mffff880001e43d40,40#5a...Ack > Packet received: > 0004e83f0288ffff0004e83f0288ffff30a680370088ffff883de4010088ffff75f13381ffffffff883de4010088ffff00a680370088ffff8005e83f0288ffff > Sending packet: $mffff880001e43d80,40#5e...Ack > Packet received: > 80c4483f0288ffff083ee4010088ffff5acd3581ffffffffe83de4010088ffff2ea70d81ffffffff401da281ffffffff40030000fffffffff500000000000000 > Sending packet: $mffff880001e43e00,40#57...Ack > Packet received: > 80c4483f0288ffff883ee4010088ffff65d73581ffffffff401da281ffffffffe04ee3460288ffffe84ee3460288ffff009380370088ffff00a680370088ffff > Sending packet: $mffff880001e43e80,40#5f...Ack > Packet received: > 0000000000000000b83ee4010088ffff7ff63581ffffffff0004e83f0288ffff460200000000000000000000000000000000000000000000d83ee4010088ffff > Sending packet: $mffff880001e43ec0,40#8a...Ack > Packet received: > 0ce83381ffffffffc09ccc3f0288ffff1500000000000000283fe4010088ffff1fc40881ffffffff489ed04f0288ffff0000000000000000083fe4010088ffff > Sending packet: $mffff880001e43f00,40#58...Ack > Packet received: > 0073d53f0288ffff15000000000000006473d53f0288ffff489ed04f0288ffff0000000000000000583fe4010088ffff68e30881ffffffff0000000000000000 > Sending packet: $mffff880001e43f40,40#5c...Ack > Packet received: > 150000000000000099000000000000001500000000000000783fe4010088ffff73520081ffffffff783fe4010088ffff0000000000000000a83fe4010088ffff > Sending packet: $mffff880001e43f80,40#60...Ack > Packet received: > 84480081ffffffffd89fd04f0288ffffd89fd04f0288ffff00000000000000000000000000000000709ed04f0288ffff53a24581ffffffff709ed04f0288ffff > Sending packet: $mffffffff8145a253,9#cf...Ack > Packet received: fa0f1f800000000065 > Sending packet: $mffffffff8145a239,1a#2c...Ack > Packet received: 1f84000000000048830424804883ec50e80287baffe8d5a5baff > Sending packet: $mffff88024fd09e70,9#6f...Ack > Packet received: 089fd04f0288ffff48 > Sending packet: $mffff88024fd09e56,1a#cc...Ack > Packet received: 0000989ed04f0288ffffe0ede4010088ffff4ea24581ffffffff > Sending packet: $mffff880001e43fc0,40#8b...Ack > Packet received: > 00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000 > Sending packet: $m0,9#02...Ack > Packet received: E14 > #0 kgdb_breakpoint (key=70, tty=0x46) at kernel/kgdb.c:1749 > #1 sysrq_handle_gdb (key=70, tty=0x46) at kernel/kgdb.c:1609 > #2 0xffffffff812b97fe in __handle_sysrq (key=103, tty=0xffff88023fef3000, > check_mask=<value optimized out>) at drivers/char/sysrq.c:522 > #3 0xffffffff812b991c in handle_sysrq (key=70, tty=0x46) > at drivers/char/sysrq.c:554 > #4 0xffffffff812b1f39 in kbd_keycode (handle=<value optimized out>, > event_type=<value optimized out>, event_code=34, value=1) > at drivers/char/keyboard.c:1204 > #5 kbd_event (handle=<value optimized out>, event_type=<value optimized > out>, > event_code=34, value=1) at drivers/char/keyboard.c:1317 > #6 0xffffffff81364180 in input_pass_event (dev=<value optimized out>, > type=1, > code=34, value=1) at drivers/input/input.c:118 > #7 0xffffffff81366151 in input_handle_event (dev=0xffff88023f3ab000, type=1, > code=34, value=1) at drivers/input/input.c:307 > #8 0xffffffff81366253 in input_event (dev=0xffff88023f3ab000, type=1, > code=34, value=1) at drivers/input/input.c:336 > #9 0xffffffff813a0ce7 in hidinput_hid_event (hid=<value optimized out>, > field=0xffff88023f388000, usage=0xffff88023f388110, value=1) > at drivers/hid/hid-input.c:646 > #10 0xffffffff8139f5b2 in hid_process_event (hid=0xffff88023ff88000, > field=0xffff88023f388000, usage=0xffff88023f388110, value=1, > interrupt=<value optimized out>) at drivers/hid/hid-core.c:875 > ---Type <return> to continue, or q <return> to quit---q > Quit > (gdb) l > 1744 void kgdb_breakpoint(void) > 1745 { > 1746 atomic_inc(&kgdb_setting_breakpoint); > 1747 wmb(); /* Sync point before breakpoint */ > 1748 arch_kgdb_breakpoint(); > 1749 wmb(); /* Sync point after breakpoint */ > 1750 atomic_dec(&kgdb_setting_breakpoint); > 1751 } > 1752 EXPORT_SYMBOL_GPL(kgdb_breakpoint); > 1753 > (gdb) p kgdb_setting_breakpoint > Sending packet: $mffffffff81bbe694,4#32...Ack > Packet received: 01000000 > $1 = {counter = 1} > (gdb) show breakpoint > (gdb) b ata_xfer_mask2mode > Sending packet: $mffffffff81310928,12#cc...Ack > Packet received: 554889e50f1f44000083c8ff0fbdd70f44d0 > Sending packet: $mffffffff81310928,1#9a...Ack > Packet received: 55 > Sending packet: $mffffffff81310929,3#9d...Ack > Packet received: 4889e5 > Sending packet: $mffffffff81310931,1#94...Ack > Packet received: 83 > Breakpoint 1 at 0xffffffff81310931: file drivers/ata/libata-core.c, line 918. > (gdb) c > Continuing. > Sending packet: $Z0,ffffffff81310931,1#dd...Ack > Packet received: E14 > Packet Z0 (software-breakpoint) is supported > Warning: > Cannot insert breakpoint 1. > Error accessing memory address 0xffffffff81310931: Unknown error 4294967295. > > (gdb) d 1 > (gdb) c > Continuing. > Sending packet: $vCont?#49...Ack > Packet received: > Packet vCont (verbose-resume) is NOT supported > Sending packet: $Hc0#db...Ack > Packet received: OK > Sending packet: $c#63...Ack > > > ------------------------------------------------------------------------------ > > _______________________________________________ > Kgdb-bugreport mailing list > Kgdb-bugreport@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/kgdb-bugreport > ------------------------------------------------------------------------------ _______________________________________________ Kgdb-bugreport mailing list Kgdb-bugreport@lists.sourceforge.net 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